Filament control system for the burning rate of a solid propellant rocket motor



May 7, 1968 R. L. GLICK 3,381,476

F'ILAMENT CONTROL SYSTEM FOR THE BURNING RATE OF A SOLID PROPELLANT ROCKET MOTOR Filed Aug. 10, 1966 Faber) L. 6//'c/r INVENTOR,

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United States Patent 3,381,476 FILAMENT CONTROL SYSTEM FOR THE BURN- ING RATE OF A SOLID PROPELLANT ROCKET MOTOR Robert L. Glick, Huntsville, Ala., assignor to Thiokol Chemical Corporation, Bristol, Pa., a corporation of Delaware Filed Aug. 10, 1966, Ser. No. 571,469 Claims. (Cl. 60--254) ABSTRACT OF THE DISCLOSURE A filament control system for the burning rate of a solid propellant rocket motor, having a plurality of tubes embedded in the solid propellant, a filament positioned in each tube with the aft ends of the tubes and the filaments being coincident with the plane of the burning surface of the solid propellant, a. pair of rollers positioned in the head end of the rocket motor and the head ends of the filaments being secured to the rollers so that upon rotation of the rollers the filaments are drawn through the tubes to control the burning rate of the solid propellant.

This invention relates to improvements for controlling the local burning rate of a solid propellant in a rocket motor and more particularly it relates to a mechanism for withdrawing filaments through the solid propellant to increase the local burning rate at the filaments and thus control the burning surface of the solid propellant.

The thrust and gas flow rate of a solid propellant rocket motor depends upon the rate of gas generation in the rocket motor at the burning surface of the solid propellant. Since the rate of gas generation is dependent upon the area of the burning surface, the thrust and gas flow rate can, therefore, be controlled by withdrawing the filaments through the solid propellant.

It is an object of the invention, therefore, to provide a controlled withdrawal of filaments from the solid propellant to increase the burning surface thereof.

The burning rate at each of the filaments is based on the rate of the withdrawal of the filament from the solid propellant. In the instant invention the filaments are withdrawn at equal rates, therefore the system is linear, since the withdrawal rate of each filament is equal. The controlled withdrawal of the filaments, therefore, provides a system where uneven burning rates along the filament are prevented, thus the increase in burning rates remain constant depending on the withdrawal of the filament.

With the above and other objects ond advantages in view, the invention consists of the novel details of construction and arrangement of parts more fully hereinafter described, claimed and illustrated in the accompanying drawing, in which:

FIGURE 1 is a schematic illustration of a solid propellant rocket motor as it will be equipped with a filament control system as embodied in the present invention;

FIGURE 2 is a fragmentary detailed sectional view of a filament and tube therefor and taken in that area bounded by the dotted circle 2 of FIGURE 1; and

FIGURE 3 is an enlarged elevational view of the control mechanism looking on the line 3-3 of FIGURE 1 with parts removed that is utilized to withdraw the filaments from the solid propellant.

Referring more in detail to the drawing, wherein like parts are designated by like reference numerals, the reference numeral in the schematic view of FIGURE 1 is used to designate a rocket motor which is equipped with the filament control system embodying the invention.

The rocket motor 10 comprises a motor case 11 having a nozzle 12 at the aft end thereof, a solid propellant 13 positioned therein, and a plenum chamber 14 at the head end thereof which is created by a suitable dividing plate 15 which may be of conventional design.

Embedded within the solid propellant and bonded thereto are a plurality of plastic tubes 'or sheaths 16 and extending through each of the tubes 16, to terminate at the burning surface 17 of the solid propellant 13, is a filament or core 18. There is a filament 18 positioned in each of the tubes 16, thus a plurality of filaments 18 extend through the solid propellant 13 into the plenum chamber 14. The filaments 18 are composed of a suitable metal which may or may not be of a combustible nature, depending upon the control of the burning rate of the solid propellant that is necessary for the rocket motor 11) to carry out its operational requirements.

The control mechanism 19, FIGURE 3, is mounted in a suitable housing 20 that is rigidly secured to the head end of the motor case 11 and the size of the housing 21 is limited to the size of the control mechanism 19 and is constructed of a material that will not add an excessive amount of weight to the rocket motor 10.

The control mechanism 19 comprises a pair of rollers 21 and 22, each of which have an annular flange 23 at the outer ends thereof. Each of the rollers 21 and 22 are also provided with stub shafts 24 that are journalled in bearing plates 25 and 26 so that there is a bearing plate at the outer ends of each of the rollers 21 and 22 and the bearing plates 25 and 26 are supported by the housing 20. The stub shafts 24 of the roller 21 have gears 27 and 28 mounted thereon intermediate of the annular flanges 23 thereon and the bearing plates 25 and 26. The stub shafts 24- of the roller 22 have gears 29 and 30 mounted thereon intermediate of the annular flanges 23 thereon and the bearing plates 25 and 26 and the gears 29 and 30 mesh with the gears 27 and 28 so that the rotagilon of the rollers 21 and 22 are as shown by the arrows 1 FIGURE 3.v

There is a pinion gear 31 that meshes with the gear 28 and is mounted on a shaft 32 that is journalled in the housing 20 and the shaft 32 may acquire power from a servo motor and any other conventional power source, not shown, that will cause suitable rotation of the shaft 32.

The filaments 18 extend, as previously stated, through the plenum chamber 14 and the free ends thereof are divided and secured to the rollers 21 and 22 by any suitable means 33.

The means for rotating the shaft 32 may be programed from a control mounted on the rocket motor 10 or it may be land based and operated after the rocket motor 10 is in flight.

The rollers 21 and 22 are of equal size and the filaments 18 are secured thereto\so that an equal pull is applied to the filaments 18 and the tubes 16 permit a smooth withdrawal of the filaments 18, since they are bonded to the solid propellant 13 and are consumed as the burning surface 17 progresses toward the head end of the rocket motor 10.

The rotation of the rollers 21 and 22 are geared to the operational requirement of the rocket motor 10 so that the speed of rotation of the shaft 32 is controlled to increase or decrease the burning rate of the solid propellant 13.

The rate of withdrawal of the filaments 18 from the solid propellant 13 will therefore give the rocket motor 10 variable thrust capability.

The operational capability of the rocket motor 10* that is equipped with a control mechanism 19, as set forth by the instant invention, depends, therefore, on the programmed rate of rotation of the shaft 32 and the equal linear withdrawal of the filaments 18.

It is believed that the foregoing description will clearly describe the operation and manner of construction of the present invention to one skilled in the art and it is also to be understood that variations therein may be adhered to providing such variations fall Within the spirit of the invention and the scope of the appended claims.

Having thus described the invention what is claimed as new and desired to be secured by Letters Patent is:

1. A filament control system for the burning rate of a solid propellant rocket motor having a solid propellant positioned therein comprising a plurality of tubes embedded in said solid propellant, a filament positioned in each tube, the aft ends of the tubes and the aft ends of the filaments being coincident with the burning surface of the solid propellant and means secured to the head or free ends of said filaments for withdrawing said filaments from said tubes to control the burning rate of said solid propellant.

2. A filament control system as in claim 1, wherein said tubes and said filaments extend longitudinally of said solid propellant in parallel relation to the longitudinal axis of said rocket motor.

3. A filament control system as in claim 1, wherein 4 the means for withdrawing said filaments from said tubes comprises a pair of rollers to which said filaments are rigidly secured.

4. A filament control system as in claim 3, wherein a power shaft is provided for rotation of said rollers and said power shaft is provided with a pinion gear therein that meshes with and controls gears mounted on said rollers for the rotation thereof.

5. A filament control system as in claim 4, wherein said rollers are provided with stub shafts that are journalled in bearing plates positioned at opposite ends of said rollers and the gears for said rollers are mounted on said stub shafts at the opposite ends of said rollers.

References Cited UNITED STATES PATENTS 3,109,375 11/1963 Rumbel et al l02102 3,128,706 4/1964 Rumbel 102-402. XR 3,136,120 6/1964 Grosh 60-2S4 3,183,665 5/1965 Webb 60254 3,286,471 11/1966 Kaplan 60254 CARLTON R. CROYLE, Primary Examiner. 

